just suggestions on type of sand to use for aluminium casting
I once had my hand cast in aluminium and they used a sand mix with a resin
that hardened with co2 (winterbond)
found a company that sells the winter bond resin what sand do I buy to use
any pitfalls would like to use this system as it seemed really simple
can get 25 litres for around £30
The sand that hardens with CO2 is fine dry silica sand mixed with 3
to 4% by weight sodium silicate (John Winter & Co Halifax) and very
thorougly mixed. For normal run of the mill work I use bagged kiln
dried sand intended for 'grouting' paving sold by builders merchants,
but use fine core sand (expensive) for small scale fine detail , and
mix it in a paddle mixer (look up Belle Tubmix) or use a plaster
mixing paddle in a drill and bucket if smaller quantities. It is very
important to make sure it is fully mixed - very easy to get unmixed
pockets that won't set. Don't try mixing with moistened sands - you'll
get a very disapointing result. I set mine using a CO2 cylinder and
regulator with a simple funnel on the end of a hose. If you want easy
breakout for fine details and cores etc mix in about 1% icing sugar
(but don't tell the wife). For open moulds for ingots etc I'll go to
the high end of the silicate addition, and for delicate stuff err on
the low side. The more you use the stronger the bond and the less
permiability you get for the gases to pass through.
When sodium silicate (waterglass) reacts with CO2 it forms crystals of
solid silica gel which is nice and hard, but of course will absord
moisture, so don't leave moulds lying about for weeks unless you bake
them before use.
The resin sands are set with a catalyst usually dispensed in correct
proportion by the sand blower in a 'proper' foundry.
I've just been out to my foundry to check, and as I suspected, my
Sodium Silicate drum is "Winterbond 80" so it ain't resin !!!!!
thanks Andrew just what I needed to know
I brought a small electric furnace on ebay and just won't to make few small
bits first if its as much fun as I remember
I may build a bigger gas version or look for a bigger electric one
but not on your scale that's scary
A friend of mine showed my his *very**first* Al-casting that he did with
oil-bound sand (I think "petro-bond" is one of the brand-names). It really
As a pattern, he used a crank case of a radial engine out of a plasic kit
(diameter about 100mm, height 50mm, bell-shaped).
You even saw the tiny hex-nuts (width about 2mm).
Wall-thickness about 1...1.5mm.
He only made some errors with the raiser and feeder and venting, so it
wasn't completely filled (20% missing).
Nick, not yet into al-casting
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